1. Field of the Invention
The present invention relates to a device attached to a conventional asphalt roller for the purpose of creating a series of depressions, typically known as rumble strips, in fresh asphalt.
2. Description of Related Art
In an effort to increase the safety of highway travel, many states utilize rumble strips to warn motorists of a hazardous situation. Typically, the rumble strips are placed on the shoulder of the road to warn motorists that they are about to veer off the road, or in the roadway itself to warn motorists of upcoming toll booths, construction, or intersections. As a vehicle drives over a series of rumble strips, the rumble strips produce noticeable vibrations in the steering column and an audible sound. Both the vibrations and the sound are useful to alert a driver who is unaware of an upcoming situation or who is drowsy and unaware of the vehicle's position on the roadway.
Rumble strips are typically formed as grooved patterns in the surface of the roadway. The two fundamental techniques used to create rumble strips are milling and rolling. The milling process involves passing a toothed milling drum over the road surface. As the milling drum rotates, the teeth thereon cut shallow radius grooves into the road surface. To properly space apart the grooves, a mechanical or hydraulic system sequentially raises and lowers the milling drum. In contrast, the rolling process involves passing over the road surface a rolling drum equipped with a plurality of radially spaced profile strips. As the rolling drum rotates, the profile strips displace still soft asphalt to form a groove corresponding in shape to the profile strips.
The related art contains several examples of devices useful for treating road surfaces. U.S. Pat. No. 4,878,713 issued to Zanetis on Nov. 7, 1989, discloses a pavement planar which is carried on the twin lift arms of a skid-steer front end loader. The pavement planar has a housing and a toothed drum which is rotatably mounted within the housing for planing operation of the road surface. A frame member is secured to the lift-arms of the front end loader, and the housing is mounted to the frame member for lateral adjustment upon a pair of guide arms and tilting adjustment about a trunnion having fore-aft axis. Depending upon whether the housing is clamped to the frame member, a single hydraulic cylinder provides for tilting adjustment of the housing about the trunnion or lateral adjustment of the housing along the guide arms.
U.S. Pat. Nos. 5,391,017 issued on Feb. 21, 1995, 5,484,228 issued on Jan. 16, 1996, and 5,607,255 issued on Mar. 4, 1997, each to Thomas et al., disclose an apparatus for cutting Sonic Noise Alert Pattern (SNAP) depressions or rumble strips in the surface of an asphalt road. The Thomas et al. '017 reference discloses the use of an eccentric member provided in direct contact with the road surface, whereby rotation of the eccentric causes raising and lowering of a cutting drum during the course of a single revolution. The Thomas et al. '288 and '255 references disclose cam member provided in direct contact with the road surface, whereby rotation of the cam member causes raising and lowering of a cutting drum as the cam surfaces of the cam member contact the road surface during the course of a single revolution.
U.S. Pat. No. 5,582,490 issued to Murray discloses a piston wheel for use on an existing cold milling machine. The piston wheel is preferably a pentagonal wheel which causes raising and lowering of a cutting head on the cold milling machine, whereby as the machine moves forward over the surface to be cut, the cutting head will be raised and lowered to produce intermittent cuts or rumble strips in the pavement surface.
U.S. Pat. No. 5,456,547 issued to Thomas et al. on Oct. 10, 1995 discloses a machine and method for forming the aforementioned SNAP type depressions in an asphalt road. The machine includes a single milling head with spaced bit sets that contact the road surface to form the depressions. The milling head is lowered to perform the necessary cutting action, the machine is advanced to effect the size of the depression, the milling head is raised to terminate the depression, and finally the machine is advanced farther to begin a new cutting procedure until a predetermined number of depressions have been formed.
U.S. Pat. No. 5,415,495 issued to Johnson on May 16, 1995, discloses a cutting machine which includes a cutting head and a drive device for driving the cutting head, as well as an engaging device for moving the cutting head out of and into contact with the road surface. The engaging device includes a hydraulic cylinder which is under control of an electronic proportional valve operated by a computer controller. The computer controller is programmed to raise and lower the cutting head as a function of the distance travelled by the machine as it moves forward over the road surface. The computer controller receives electrical impulses from a conventional wheel mounted encoder.
In the article Ready to Rumble appearing in the March 1997 issue of Asphalt Contractor, the article indicates that rolled rumble strips may be formed by an attachment drum on the roller or by mounting bars on a drum roller. The article continues by suggesting that the attachment is not a full machine, but is instead controlled with an hydraulic arm. The article makes no suggestion for using more than one hydraulic arm.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.